Syringe

ABSTRACT

The invention relates to a syringe (1) which comprises a rod (5) mounted for reciprocating movement in relation to a container (8), wherein one end of the rod has the form of a needle (3) or is able to coact with a needle. The syringe further comprises a piston (4) and coupling member (6) which connect and disconnect the piston to and from the rod. The coupling member assumes a connecting state when the piston is drawn by the rod from a position proximate to the needle to a position in which it is distanced therefrom, and are brought to a disconnecting or disconnected state when the piston is pressed by the rod towards the needle. The coupling member comprises support and/or slide surfaces (5k&#39;, 5k) arranged on that part of the rod which is proximal to the needle, and opposing support and/or slide surfaces (4k&#39;, 4k) on the piston. The first support and/or slide surfaces (4k&#39;) provided on the piston and located nearest the needle (3) are inclined (c) to an extent such that as the rod (5) moves towards the needle (3), the piston (4) is rotated about a container center line, among others.

TECHNICAL FIELD

The present invention relates generally to a syringe and moreparticularly, although not exclusively, to a syringe which is intendedfor one time use only, i.e. a so-called disposable syringe, and which isof the kind that includes a rod which is fitted in a container forreciprocating movement in relation thereto and one end of which has theform of or coacts with a needle, a piston which is able to coact withthe rod, and coupling means which function to connect and disconnect thepiston to and from the rod.

The present invention is primarily intended to provide a syringe of thiskind which is constructed so as to enable the container to be filledwith liquid through the needle and the liquid then dispensed throughsaid needle and so that after this the container can no longer be filledwith and emptied of liquid.

The present invention pertains in particular to a syringe of the kind inwhich the coupling means which function to connect and disconnect thepiston to and from the rod adopt an active coupling state over amovement path in which the piston is drawn by the rod from a positionclose to the needle to a position in which it is distanced from saidneedle, and is brought to a disconnected state when the piston ispressed by the rod through an adapted short movement path in a directiontowards the needle, said coupling means comprising support and/or slidesurfaces which are provided on that part of the rod which lies proximalto the needle and which coact with opposing support and/or slidesurfaces on the piston in the coupled state of the rod and the piston.

BACKGROUND ART

Disposable syringes of the aforedescribed kind, by which is meantsyringes that can only be used once, can be divided into a number offunction-dependent categories with regard to their function-dependentcharacteristics.

A first syringe category is exemplified by the syringe illustrated anddescribed in the International Patent Publication PCT/SE88/00634,International Publication No. WO 89/04677. In the case of this syringe,the rod can be twisted in relation to the container and the piston so asto move the coupling means on the one hand to a connecting state and onthe other hand to a disconnecting state, as the rod is twisted. Thus,with this type of syringe, it is necessary that the piston is unable totwist or rotate or at least not essentially, at the same time as the rodis twisted in relation to the container.

It is thus of great importance with this category of syringe that meansare provided to ensure that the piston will not twist together with therod.

In a second syringe category, the rod, or red unit, carries a piston orpiston unit and moves backwards and forwards in the container withouttwisting, and the outer surface of the piston unit and the inner surfaceof the container include means which mutually coact to lock the pistonin a lowermost position. Examples of these prior art syringe assembliesare described and illustrated in prior publications U.S. Pat. Nos.4,391,272; 4,775,364; PCT/GB87/00728 with respective InternationalPublication Nos. WO 88/02640; GB-A 2,197,792 and FR-A 2,613,628.

A third category of disposable syringes includes a rod unit which ismoved forwards and backwards in the container without twisting, and apiston unit which is fastened to the rod unit by means of a separateconnecting part.

This connecting part is pivotally mounted on the rod part for rotationabout a centre line on the rod, the piston and the container, and can beguided into to different rotational positions by grooves disposed on thepiston unit.

An example of this type of syringe is described and illustrated inpublication NO-A 163,263.

DISCLOSURE OF THE PRESENT INVENTION TECHNICAL PROBLEMS

When studying the earlier known art as described above, whileconsidering the comprehensive efforts that have been made to construct adisposable syringe which is well adapted for mass production at a costwhich is comparable with the cost of manufacturing standard reusablesyringes, it will be seen that a qualified technical problem is one ofrealizing the possibility of moving the coupling means for connectingand disconnecting the piston to and from the rod to a desired connectingand desired disconnecting state or position, solely by providingconditions which will enable the piston to be rotated within thecontainer.

Another technical problem is one of realizing the significance ofproviding conditions such that rectilinear movement of the rod in thecontainer towards the needle, without twisting the rod, will causedesired rotation of the piston so that the piston unit will cease tocoact with the rod unit upon restricted rotational movement, such asrotation through less than one-half revolution.

Another technical problem is one of realizing the significance ofadapting the supporting and/or sliding surfaces on the piston unitand/or the rod unit and by inclining said surfaces at an appropriateangle.

A further technical problem is one of realizing the significance ofadapting the configuration of the opposing support and/or slide surfacesso as to adapt said surfaces to a desired degree of friction, and/or toa form in which they can be conveniently produced in a mould die.

Still another technical problem is one of realizing the advantages thatare gained with regard to the operation of a syringe which is soconstructed that when the piston is moved towards the needle so as toinject liquid contained in the container, the piston will generate awell-defined frictional force against the inner wet surface of thecontainer, and therewith to realize the significance of choosing anappropriate angular value while considering the occurrent readilydefinable frictional conditions.

It will also be seen that a technical problem resides in realizing thesignificance of allowing the first support and/or slide surfacesprovided on the piston proximal to the needle to slope at such an anglethat as the rod is moved towards the needle, the piston will be twistedabout a centre line on the container, among other centre lines, so as tobring said coupling means from a connected to a disconnected state inresponse to movement of the rod along a short movement path.

It will also be seen that a technical problem resides in realizing thesignificance of inclining said surfaces faces such that as the piston isrotated by the mutually coacting surfaces over a chosen initial movementpath, which at least equals less than half the maximum movement path ofthe rod in the container, the first support and/or slide surfaces on thepiston will be distanced from corresponding first support and/or slidesurfaces on the rod to a position in which the coacting surfaced of saidcoupling means are disconnected.

It will also be seen that a technical problem resides in realizing thesignificance of displacing the piston and the rod to a mutuallydisconnected position over a small distance of less than one-quarter ofthe maximum movement path of the rod while still providing the desiredfunction.

Another technical problem is one of realizing the significance ofconfiguring the first support and/or slide surfaces on the rod so thatsaid surfaces will coact selectively with corresponding first supportand/or slide surfaces on the piston, wherein said contact surfaces canbe either flat surfaces or linear surfaces, or alternatively punctiformsurfaces, where at least the two latter surfaces shall slide against acontinuous, preferably curved slide surface.

Another technical problem is one of realizing the significance ofinclining the first support and/or slide surfaces on the piston and/oron the rod at a well-adapted angle to a centre line on the piston or therod, among others.

A further technical problem is one of realizing the significance ofinclining the second support and/or slide surfaces that are provided onthe piston distal from the needle at an angle such that as the rod ismoved away from the needle, the piston will be subjected to a forcewhich acts on the second support and/or slide surfaces on the rod suchas to rotate the piston around a container centre line, said secondsupport and/or slide surfaces holding the corresponding second supportand/or slide surfaces in a mutually coacting or mutually engagingposition.

Another technical problem is one of realizing the significance ofadapting the configuration of the second support and/or slide surface onthe rod to the second support and/or slide surface on the piston.

When considering the aforesaid circumstances, it will also be seen thata technical problem resides in the ability to choose angular limitvalues which will not only ensure a desired and positive aspirationfunction but also a positive function with respect to the remainder ofthe disposable syringe.

SOLUTION

With the intention of solving one or more of the aforesaid technicalproblems, the present invention departs from a syringe of the kind whichincludes a rod that can be moved reciprocatingly in relation to acontainer and one end of which is in the form of a needle or is intendedto coact with a needle, and which further includes a piston which coactswith the rod, and coupling means for connecting and disconnecting therod to and from the piston.

The coupling means which function to connect and disconnect the pistonto and from the rod are mutually engaged when the piston is drawn by therod from a needle-proximate position to a needle-distanced position, andis brought to a disconnecting and disconnected state when the piston ispressed initially by the rod through an adapted short movement path in adirection towards the needle, said coupling means comprising supportand/or slide surfaces on that part of the rod which is proximal to theneedle and corresponding opposing support and/or slide surfaces on thepiston, said surfaces coacting mutually in the coupled state of saidcoupling means.

In accordance with the invention, the first support and/or slidesurfaces of the piston located nearest the needle are inclined to anextent such that as the rod is moved initially towards the needle, thepiston is rotated about a container centre line, among others.

According to preferred embodiments that lie within the scope of theinvention, the extent to which the piston is rotated by the inclinedsurfaces is adapted so that during said rod movement and after movementalong a short movement path, which is less than half the maximum path ofmovement of the red in the container, the first support and/or slidesurfaces on the piston will leave the corresponding first support and/orslide surfaces on the rod so as to bring said coupling means to adisengaged state.

The angle at which said surfaces are inclined is preferably so adaptedthat the distance through which the red moves in order to achieveaspiration can be chosen to be smaller than one-quarter of the maximumdistance moved by the rod in the container.

According to one embodiment, the first support and/or slide surfaces onthe rod may be configured for parallel, linear or punctiform cooperationwith corresponding first support and/or slide surfaces on the piston.

It is especially preferred that the first support and/or slide surfaceson the piston and/or on the rod define an angle of between 85° and 20°with a centre line on the piston or the rod, among others.

One advantage afforded by the present invention is that the rod, in aknown manner, can now be made straight and adapted for movement up anddown in the container without twisting, with the inclusion of anassociated simplified rod attachment and rod guide in the uppercontainer part.

Furthermore, the second support and/or slide surfaces on that part ofthe piston which is distal from the needle are inclined to such anextent that as the rod is moved away from the needle, the piston will besubjected to a force which causes the piston to be rotated around acontainer centre line, among others, by the second support and/or slidesurfaces on the rod, these latter surfaces holding the piston and itscorresponding second support and/or slide surfaces in a coacting orco-engaging position.

According to one embodiment, the second support and/or slide surfaces onthe rod are configured for parallel, linear or punctiform coaction withcorresponding second support and/or slide surfaces on the piston.

ADVANTAGES

Those advantages primarily associated with an inventive disposablesyringe are that the aforesaid coupling means remains in a coupled statewhen the piston is drawn by the rod from a position proximate to theneedle to a position distanced therefrom, and are brought to adisconnecting or disconnected state when the piston is then pressedinitially by the rod towards the needle, in that during axial movementin the container along a short displacement path, the first supportand/or slide surfaces coacting on the piston and the rod will cause thepiston to rotate so as to cause said coupling means to take adisengaging position, this being achieved solely by adapting the slopeof the first support and/or slide surfaces in relation to a pistoncentre line or a container centre line, among others.

The primary characteristic features of an inventive disposable syringeare set forth in the characterizing clause of the following Claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplifying embodiment at present preferred and having propertiessignificant to the present invention will now be described in moredetail with reference to the accompanying drawings, in which

FIG. 1 is a perspective view of the lower part of a rod and associatedsupport and/or slide surfaces, and a piston with associated supportand/or slide surfaces, and shows said surfaces ill a mutually distancedand mutually disengaged position;

FIG. 2 is a side view showing flat support and/or slide surfaces on therod in engagement with flat support and/or slide surfaces on the piston,with the illustrated angular values being related to a centre line onthe piston and the rod, among others;

FIGS. 3-5 are side views of alternative configurations of the supportand/or slide surfaces on the rod;

FIG. 6 illustrates a linear coaction surface between the support and/orslide surfaces of the piston and the rod; and

FIG. 7 illustrates a punctiform coaction surface between the supportand/or slide surfaces of the piston and the rod.

BEST MODE OF CARRYING OUT THE INVENTION

Because the inventive syringe can be considered to constitute a directdevelopment of the disposable syringe illustrated and described inInternational Patent Publication PCT/SE92/00258, reference is made tothis publication for a closer description of the different components ofthe syringe and the manner in which they coact with one another.

To simplify matters, the same reference signs as those used in theaforesaid international patent publication have been used in the presentdrawing to identify similar components.

Thus, it can be seen that the present invention is based on a syringe 1which comprises a rod 5 that can be moved reciprocatingly in relation toa container. One end of the rod 5, the lower end, has the form of aneedle 3 (not shown) or is able to coact with said needle, a pistonwhich coacts with the rod, and coupling means 6 which function toconnect and disconnect the piston to and from the rod.

As shown in FIGS. 2-7, the opposing surfaces of the coupling means 6 aremutually engaged as the piston is drawn by the rod from a positionproximate to the needle 3 to a position in which the piston is distancedfrom the needle, and are disengaged when the piston 4 is pressed by therod towards the needle 3. In the case of the first mentioned movement,the part 5a' is located further to the right than is shown in theFigures.

FIG. 1 illustrates an operational state of the syringe in which thepiston is located in its lower-most position upon completion ofinjecting the contents of the syringe, with the rod withdrawn slightlyupwards without coacting with the piston.

The coupling means 6 is comprised of support and/or slide surfacesprovided on that part 5a' of the rod which is proximal to the needle,and coacting, opposing and corresponding support and/or slide surfaceson the piston.

FIG. 2 illustrates clearly the significant characteristics of thepresent invention, wherein the first support and/or slide surfaces 4k'provided on the piston 4 and located proximal to the needle 3 slope tosuch an extent that as the rod 5 is moved towards the needle 3, thepiston 4 is rotated about a centre line 5' of the container 8, the rod,or the piston.

Naturally, rotational movement of the piston 4 in response to axialmovement of the rod 5 will depend to a very large extent on the angle atwhich the support and/or slide surface 4k' are inclined. According tothe present invention, the slope of said surfaces is adapted so that thefirst support and/or slide surfaces on the piston will move away fromthe corresponding first support and/or slide surfaces on the rod over achosen short movement path, which is shorter than half the maximummovement path of the rod in the container 3, so as to mutually disengagethe coupling means. This is shown in broken lines in FIG. 2.

The aforesaid movement path is conveniently chosen to correspond to adistance which is shorter than one-quarter of the maximum movement pathof the rod, for instance a movement path which is shorter than 10 mm,normally somewhat shorter than 5-7 mm, to provide an aspiring function.

The first support and/or slide surfaces 5k' on the rod are configured soas to be parallel with the corresponding first and/or slide surfaces 4k'on the piston, as clearly shown in FIG. 2.

There is nothing to prevent the slide surfaces 4k and/or 4k' from beingcurved, however, although the curve will preferably be continuous.

It is particularly recommended that the first support and/or slidesurfaces on the piston and/or on the rod define an angle "c" of between85° and 20° with a piston centre line or rod centre line 5'.

This angular value lies within those limits within which a practicalfunction can be obtained, and a longer aspiration path is obtained atthe lower values.

The surfaces may also be sloped at an angle which is adapted to therequisite sliding function.

A suitable angular value is between 80° and 45°, preferably between 75°and 65°.

FIG. 1 shows an angular value of about 80°, whereas FIGS. 2-5 show anangular value of about 70°.

The rod 5 is straight and is adapted for rectilinear, reciprocatingmovement in the container 3 without twisting.

The second support and/or slide surfaces 4k located on the piston distalfrom the needle 3 slope to an extent such that in coaction with thesecond support and/or slide surfaces 5k on the rod, the piston will besubjected to a force which causes the piston to rotate about a containercentre line, among other centre lines, as the rod 5 is moved away fromthe needle, wherein the second support and/or slide surfaces 5k on therod hold the corresponding second support and/or slide surfaces 4k in amutually coacting or mutually engaging position.

In the case of the FIG. 2 embodiment, the second support and/or slidesurfaces 5k on the rod are parallel with the corresponding secondsupport and/or slide surfaces 4k on the piston.

The angle "c" and the length of the groove can thus be chosen inaccordance with the desired maximum aspiration length of the rod, amongother things, and the maximum movement path desired between fullycoacting or fully engaged position of the coupling means 6 and aguaranteed disengagement position.

The angle "c" shall thus be chosen so that as the rod 5 is moved awayfrom the needle 3, the piston will be rotated into a fully coactingposition, as illustrated by the position 4k".

In the exemplifying embodiment, the angular values "c" and "c'" areidentical, although there is nothing to prevent these angles beingdifferent to one another.

It should be noted in this regard that as the piston 4 is moved towardsthe needle 3, the peripheral surface of the piston will slide along wetinternal container surfaces, and that well-defined frictional conditionsprevail during this movement of the piston, these conditions beingobserved primarily when choosing tile value of the angle "c".

When moving the piston 4 away from the needle 3, the piston will slidealong dry surfaces and the frictional conditions are more difficult todefine. This circumstance should be taken into account when choosing thevalue of the angle "c'".

FIG. 3 illustrates an embodiment in which the support and/or slidesurface 5k' on the rod provides a linear or punctiform abutment surfacewith the flat or angled first support and/or slide surface 4k' on thepiston.

The second support and/or slide surface 5k on the rod is flat and cancoact with a flat or linear abutment surface against the second supportand/or slide surface 4k on the piston.

FIG. 4 illustrates an embodiment in which the support and/or slidesurfaces on the rod 5 provide linear or punctiform abutment surfaces 5k'and 5k, corresponding to the configuration of the support and/or slidesurfaces on the piston 4.

The embodiment illustrated in FIG. 5 includes a flat first supportand/or slide surface 5k' and a linear second support and/or slidesurface 5k.

In the case of the FIG. 6 embodiment, the first and second supportand/or slide surfaces 4k' and 4k on the piston 4 are flat and parallel,whereas in the FIG. 7 embodiment the surfaces 4k' and 4k are flat andinwardly converging. (There is nothing to prevent the surfaces fromconverging outwards).

As will be understood, it is conceivable within the scope of theinvention to combine each detail in FIGS. 2-5 with each detail in FIGS.6 and 7.

Depending on the chosen angle "c", it can be assumed that in the case ofsmall angular values, the piston is able to rotate without movinglongitudinally or while moving only slightly in a longitudinaldirection, whereas in the case of large angular values, the piston willrotate whilst moving in a longitudinal direction.

The invention is based on forcibly guiding movement of the rod in thecontainer in a manner which makes it impossible to rotate or twist therod in relation to the container and therewith effect unpermittedengagement and disengagement of the coupling means 6, irrespective ofwhether the rod is moving or stationary.

The guide means herefor may conveniently be mounted within the open partof the container distal from the needle 3.

It will be understood that the invention is not restricted to theaforedescribed and illustrated exemplifying embodiments thereof and thatmodifications can be made within the scope of the invention defined inthe following Claims.

I claim:
 1. A syringe comprising:a container having a center line, apiston end, and a needle end; a rod which can be moved reciprocatinglywithin the container; a piston which coacts with the rod, and couplingmeans for connecting and disconnecting the piston to and from the rod,said coupling means assumes a connected state when the piston is drawnby the rod from a position proximate to the needle end toward the pistonend, and the coupling means is brought to a disconnected state when thepiston is pressed by the rod towards the needle end, said coupling meansincludes surfaces on a part of the rod which is proximal to the needleend and includes opposing and coacting surfaces on the piston, a firstone of the surfaces located on the piston is inclined at an inclinationto an extent such as to cause the piston to rotate about the center lineas the rod moves towards the needle end.
 2. A syringe according to claim1, wherein the inclination is such that as the rod moves towards theneedle end a distance less than one-half of a maximum movement path ofthe rod in the container, the piston will rotate so as to disengage thefirst surface on the piston from a corresponding first one of thesurfaces on the rod and therewith bring the coupling means to thedisconnected state.
 3. A syringe according to claim 2, wherein saiddistance is less than one-quarter of the maximum movement path of saidrod.
 4. A syringe according to claim 3, wherein one of the surfaces onthe part of the rod is configured for parallel, linear or punctiformcoaction with the first surface on the piston.
 5. A syringe according toclaim 2, wherein one of the surfaces on the part of the rod isconfigured for parallel, linear or punctiform coaction with the firstsurface on the piston.
 6. A syringe according to claim 1, wherein one ofthe surfaces on the part of the rod is configured for parallel, linearor punctiform coaction with the first surface on the piston.
 7. Asyringe according to claim 1, wherein one of the surfaces on the part ofthe rod defines an angle of between 85° and 20° with the center line. 8.A syringe according to claim 1, wherein the rod is straight and ismounted so as to move reciprocatingly in the container without twisting.9. A syringe according to claim 1, wherein a second of the surfaces onthe piston is located distal from the needle end and is so inclined thatas the rod is moved away from the needle end a second of the surfaces onthe rod subjects the piston to a force which rotates the piston aboutthe center line.
 10. A syringe according to claim 9, wherein the secondsurface on the rod is configured for parallel, linear or punctiformcoaction with the corresponding second surface on the piston.
 11. Asyringe according to claim 1, wherein the first surface on the pistondefines an angle of between 85° and 20° with the center line.